QuestionQUESTION: harness at coil to engine melted against exhaust crossover. Taped separated wires,repositioned, engine now runs perfectly, except no a/c. Disconnect/reconnect hi-lo sw, fans come on high,no clutch. Did the wires all touching damage the module? Is the P1598 code indicative of internal module damage?
ANSWER: Hi Eli,
The pressure sensor switch "signal" voltage is too high according to the 1598 code. The signal wire is light blue/brown and runs from pin 3 of the sensor to pin 42 of the #2 plug (gray/gray) on the pcm. The normal voltage range on that wire should be 0.5 to 4.5 volts depending upon how much refrigerant is in the system, so anything above 4.5 would cause the code. It could be the wire is shorted to a 5 volt wire that also goes to the sensor (pink/yellow) that comes from pin 61 of that same plug and is on pin 2 of the sensor plug, or it could be shorted to an 8 or 12 volt wire in the melted harness. So unplug the sensor and see what the reading on the pin 3 (blue/brown wire. If it is 5v then see if you can find a short to the pink/yellow wire. If it is a different voltage let me know which it is.
Roland
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QUESTION: Roland, thank you for your concise nswer. The voltage is 4.7, with engine running battery voltage at 14. There isn't any place the wires are now touching, each taped where the insulation had melted. All the copper was in actual contact, not grounded to the engine,as it had not yet burned through the woven sheath that holds that harness. As I was manipulating that harness before finding the problem, the A/C did engage, but not as I let go.
With the hi-lo disconnected, the fans go to high.
ANSWER: Hi Eli,
I assume that you measured the voltage on the wire while the plug was inserted in the pressure switch so that it was telling you the reading of the switch signal. I haven't found specifics for the 1598 code other than the signal is too high. At 4.7V that would be too high for the go ahead to operate the compressor clutch. Was the refrigerant recently "topped-up"?
Might the 1598 be a stale code from the time of the original melt? Did you disconnect the battery to erase the codes, and still get this code? What is the "hi-lo" which you disconnect to impact the fans?
Roland
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QUESTION: Roland, Good Morning,
No, I disconnected the pressure (hi-lo) switch connector to make the measurement.and yes, when the a/c was blowing warm last week, I did top it, but when seeing 1598, I assumed to high, and removed some freon, with no improvement. I've used a scanner to erase codes, and while servicing, did have battery disconnected. I'm going to probe the PCM side of the harness now,and hope to have the right reading. I'll leave the hi-lo connected while probing.
AnswerHi Eli,
The light blue/brown wire is the signal wire which reports the pressure to the PCM and so if you unplug it to make the reading I would suspect there to be little or no voltage on it as you are then "looking" at the input to the pcm which is looking to find the voltage on the wire when it is plugged in. So I would believe that the wire is shorted to a 5v supply wire.
Roland
